What am I so afraid of?

I'm not an idiot. I know that if I keep going the way I am that I will have a heart attack, weigh 400 pounds, have diabetes and be miserable. I know that I am slowly killing myself with the foods I eat and the lack of exercise. I also know what I should do to fix it. I know what foods are healthy. I know I need to be more active. Why can't I just do it? Sure I have some really good excuses. I have a bad back. I'm battling depression. I'm allergic to heat. (I break out into hives when I get really hot.) I also know that more than excuses, they are REASONS to change my ways. It is so difficult. I don't know what is stopping me from changing. Actually I do know. I'm afraid. I'm afraid to fail. Again. I'm afraid of losing things that bring me joy. I'm afraid it will change my relationships. I'm scared of the work that I'll have to do. I'm afraid that I won't be able to handle the stress of making such a major change in my life. I'm afraid that I won't have support from family and friends. I'm scared that I'll become even more crazy than I already am. How do I overcome these fears?